Article press method and apparatus for pulp molding machines



Nov. 22, 1966 w. s. PEPPLER 3,287,208

ARTICLE PRESS METHOD AND APPARATUS FOR PULP MOLDING MACHINES Filed Nov. l5. 1963 /2 H6. 1 (y /10 ,2 Z2

falli-IE INVENTOR W/'l//kzm S. Papp/er KARL (35A. :Hocus ATTORNEY United States Patent Oi.

3,287,208 Patented Nov. 22, 1966 ice 3,287,208 ARTCLE PRESS METHOD AND APPARATUS FOR PULP MOLDING MACHINES William S. Peppler, Chappaqua, N.Y., assigner to Diamond International Corporation, a corporation of Dela- Ware Filed Nov. 15, 1963, Ser. No. 324,082 7 Claims. (Cl. 162-227) This invention relates to a pulp molding method and apparatus and more particularly to a device for rapidly molding compacted pulp articles having an essentially completely smooth outer surface and Without the necessity of employing complex mating dies.

When suction molded pulp articles are formed, the surface of the articles not in contact with the mold are produced with a rough and uneven configuration; these characteristic bumps are made by bundles of fibers and are due to evacuation of water from between the pulp fibers. It is desirable to obtain a smooth surface rather than the rough and uneven surface in order to provide a more attractive product. In addition, it is desirable to compress the rough pulp article in order to provide a denser and stronger article.

In the past these ends have been obtained by lirst forming the article and then subsequently applying pressure to the article by the use of accurately formed mating dies. Such mating dies, having a smooth surface in the form of the configuration desired on the molded pulp article, have been provided adjacent the molding drum so that the mating dies come in contact with the rough surface of the de posited pulp article While such article is still on the suction mold and after the mold has been withdrawn from the pulp slurry. Such mating dies have been made of metal or rubber. The dies according to this prior practice are expensive to provide and necessitate in their operation a reduction in product output due to reduced operating speeds. In addition, such mating dies generally require the use of complex registry apparatus.

Another prior art practice of compressing and smoothing the molded pulp product comprises removing the molded pulp article from the suction die and then pressing it between hot matching dies. This practice suffers from the same problems and disadvantages as the system of the preceding paragraph.

It has also been proposed to use a stretchable belt adjacent the uneven surface of the molded pulp article while the article remains on the suction die; in this manner vacuum is applied through the pulp article to the stretchable belt which is then sucked in against the rough and uneven surface to effect a smoothing. This practice, although reducing the cost of equipment, has failed to produce a satisfactory product as desired. All of the known prior art methods of smoothing molded pulp articles start with a comparatively rough surface which is characteristic of the texture of molded pulp.

The present invention contemplates obviating the aforementioned problems by eliminating the characteristic bumps before they are formed and by compressing the article while it is still in a soft and moldable condition. This is accomplished by applying pressure to the pulp deposit on the pulp mold While the deposit is still in a Wet and gelatinous stage beneath the surface of the pulp slurry. The pressure applying means comprises a series of hard, elastic and deformable plugs having a surface configuration complementary to the surface configuration of the pulp molds and which mate with the molds while still in the slurry to squeeze and compress the pulp deposits on the molds. i.

It is therefore an object of the present invention to provide an improved method and apparatus for producing smooth surfaces on molded pulp articles.

It is another object of the present invention to provide an improved and novel method and apparatus for producing a compressed pulp molded article of improved strength.

It is another object to provide a method and apparatus for producing molded pulp articles having greater strength, hardness, density and uniformity.

It is yet another object of the present invention to provide an apparatus which is simple and economical to produce and yet which may be used with conventional pulp molding equipment without reducing the rate of production of molded pulp articles.

It is another object of the present invention to provide an apparatus which operates simply and quickly without the need for ancillary registry equipment.

It is another object of the present invention to provide a method and apparatus which improves the rate and uniformity of drying of molded pulp articles thereby increasing the production rate and reducing the warpage of articles on drying.

Other objects and the nature and advantages of the instant invention will be apparent from the following description taken in conjuncntion with the accompanying drawings, wherein:

FIG. 1 is a fragmentary view showing the apparatus of the present invention.

FIG. 2 is a view of a pressure applying means accord- Ving to the present invention taken along line 2 2 of FIG. 1.

FIG. 3 is a sectional view of a pressure applying means taken along line 3 3 of FIG. 2.

Referring more particularly to the drawing, there is shown generally in FIG. 1 a molding drum 10 comprising a central core 12, a plurality of hollow spokes 14 passing from the core 12 to the periphery of the drum, and a plurality of pulp molds 16, each provided at the end of a hollow spoke 14. Beneath the molding drum 1i) is a pulp slurry vat 18 which contains a pulp slurry stock 20 through which the submerged pulp molds 16 travel. In a manner well known in the art, the drum is rotated while vacuum is applied through pulp molds 16; this effects deposition of pulps on each mold 16 as it passes through the pulp stock 20. During rotation of the drum, each mold 16 may rotate through a series of stations including a pulp depositing station, a pressure applying station, a drying station and an article removing station. The present invention relates to the pulp depositing and pressure applying stations.

Each mold 16 is formed of a perforated material and covered with a screen as is well known in the prior art. As a mold 16 passes through slurry 20 vacuum is applied through to hub 12, the hollow spokes 14, and nally Vthrough the perforated mold 16 to effect deposition of pulp upon the screen of the mold. Conventionally, as pulp forms on the die and water drains out of the pulp, the wood fibers tend to aggregate into bundles with the water draining through passageways of least resistance formed between the bundles. During the formation of the article under the surface of the slurry, however, the water acts as a carrier Ifor the even distribution of iibers, since conventionally there is rabout 99 parts of -wa-ter 'for each part of liber in the stock slurry 20. Thus, due to the high Water to lfiber ratio, distribution of libers Iand draining of water fnom the pulp deposit will be essentially uniform while such deposit is in the slurry. The instant the mold 16 comes out of the slurry 20 however, the gelatinous pulp held to the mold by vacuum stillhas so much water in it that the fibers are .still well dispersed. It is -only after the bulk of the water is drained out that the fibers tend to aggregate together and for-m the characteristic bumps.

To prevent the bers from aggregating together to form the characteristic bumps andto further-effect compression of the molded pulp article while it is still in a c-ompressible and imoldable state, a pressure applying means shown generally at 22 is provided to initiate compression of the pulp deposit while it is still beneath the surface of the stock slurry 20. The articles produced after being compressed by pressure applying means 22 are very dense, strong and smooth and, when removed from the die are much drier than articles `of the prior art. By applying pressure while the deposited pulp is still in the lgela-tinous and water draining stage, the fibersy stay -dispersedand form uniformly `over the pulp 'molds 16. Besides greatly densifying the ultimate article and providing an article strength on the average of` twenty percent lgreater than any articles of the prior art, the pressure applying means provides an exceptionally smooth surface on the entire outer surface of the molded pulp article.

The pressure applying means 22` of the present invention comprises a series of plugs 24 each having an inner surface 26 which is complementary in shape to the outer surface of the pulp molds 16. The plugs 24 are comprised of a material -which is sufliciently hard to maintain its desired surface configuration 26 durin-g molding but, on the other hand, is sufficiently elastic and deformable to iiex under strain so that .the plug may be broken away from the vacuum exerted through the mold and product after the desired pressure application. In other words, the material from which the plugs 24 are formed must be hard enough to properly exert pressure and to provide a -true and accurate shape to t-he outer portion of the plup deposit, but, -on the lother hand, must be ilexible enough so that when pulled away ,from the mold to which it is attached by suction, the plug 24 will bend suciently t-o allow air to enter its sides and thus break the vacuum. A suitable material has been found to be polyurethane. Other materials, such :as stiff natural or synthetic rubber may be used.

Each plug 24 is provided between two endless chains 28 and 30 each of which is aligned on and passes about two rotating chain sprockets; as seen in FIG. 1, chain 28 passes about the Ktwo chain sprockets 32 a-nd 34. Thus sprocket 34 and its equivalent for chain 30 are disposed within the pulp slurry while sprocket 32 and its equivalent for chain 30 are disposed above the exit end of the vat 18. In order for the plugs 24 to mate accurately and properly with the molds 16, the distance between each mold 16 must be uni-form; due to present product take-off equipment such uniformity is conventional. Thus, by simply providing an equal and uniform space between each plug 24, a plug 24 and a mold `16 will mate uniformly and consistently without the necessity of any complex registry equipment. For this reason it is necessary that the plugs 24 be `accurately spaced and accurately maintained both along and between the chains 28 and 30.

In the illustrated embodiment the plugs 24 :are attached to the chains 28 and 30 by passing bolts 36 and 38 through each chai-n and through a plug 24 s-o that the chains 28 and 30 are contacted by the extremities of the bolt :and the plug .is contacted in the middle of the bolt. In order to allow the passage of the bolts 36 and 38 through the plug 24, each plug is provided with two laterally directed holes 46 and 48. Thus bolt 38 passes through hole 48 Iat one longitudinal end of each plug 24 and bolt 36 passes hole 46 at the other end of each plug. Holes 46 and 48 are provided with a somewhat eliptical cross-section so that the plug 24 may move 1ongitudinally (transversely to the direction of the bolts 36 and 38) in a manner similar to a lost motion hinge. This lost motion hinge assembly is necessary as the plugs 24 pass around the sprockets 32 land 34. In addition, such -a lost motion action will permit registry of a plug 24 on a .mold 16 by self-seating in cases where the -molds and plugs are slightly out of registry. Spacers to turn freely on the idle sprockets such as 32 vand 34 and are driven by the movement of the molds in engagement with the plugs 24. Alternatively, the sprockets such as 32 and/or 34 may be driven, but this requires the ruse of synchronizingregistry equipment. It is necesi sary lfor the chains 28 and 30 lto be relatively tightly stretched so that the plugs 24 come into tight contact with the molds 16 to provide full and uniform contact of the gelatnous surface-of the pulp deposits by the plugs 24 without trapping any air. therebetween. The contact must also be tight so that the plugs will exert the necessary pressure t-o provide the desired smoothing and compactin-g. Therefore, means` `for adjusting the tension (not shown) of the chains may be provided, such as, for example, lmerely providing one set of sprockets 32 movable away from and towards the other set 34.

As a mold.16 advances through steps A and B (note FIG. l), pulp is deposited freely on the mold 16.` Between steps B and C the mold 16 comes in contact with a plug 24 and at step C the gelatnous pulp deposit is pressed uniformly by such plug 24. The pressure exerted by the plug 24 is continued through step D where the mold has emerged from the stock slurry and between steps D and E the mold 16 is pulled away from the plug 24. Thus as the mold rotates through steps C and D the pressure exerting plug 24 moves along with the mold 16 and continues to exert force which tends to squeeze water out of the pulp deposit. This squeezing action, along with the vacuum applied from the other side of the pulp article through the mold removes most of the water in the pulp deposit. Shortly after the plug has come in contact with the gelatnous pulp deposit and has shielded that deposit from the remainder of the pulp slurry, the suction behind the mold 16 becomes effective on the plug to pull the plug into even tighter contact with the pulp deposit; such suction does not become effective until the majority of the water has been pulled from the pulp deposit and the pulp deposit is no longer gelatnous. Thus between steps D and E, when the plug becomes separated from the mold 16, it is necessary to break the vacuum connection between the plug 24 and the mold 16 and at this point the exibility of the plug 24 enables the plug to bend su'iciently so that air may enter between the plug 24 and the mold 16 in order to break the Vacuum.

It is essential in the present invention that pressure be applied to the pulp deposit while it is still in its moldable and gelatnous stage. If the pressure application is held up until vacuum is drawn through the deposit and the water is displaced by air, i.e. shortly after the'mold has left the stock slurry 20, the deposit willhave already obtained its characteristic bumps and, in addition, it will be impossible to apply the type of compression which will compact the deposit suiciently to provide the increased also contemplates a drum placed horizontally and revolving about a vertical axis. If desired, other systems, rather than a continuous and/ or intermittent rotating drum with molds about its periphery, may be used.

It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification but only as indicated in the appended claims.

What is claimed is: 1. In the method of suction molding pulp articles wherein'a Series of Shaped pulp molds is passed through a vat containing a slurry of pulp and wherein vacuum is applied to the molds to effect the deposition of pulp thereon and comprising applying pressure to the pulp deposit on each shaped mold in sequence while said pulp deposit is submerged beneath said pulp slurry, and maintaining application of pressure until said each mold has passed out of said pulp slurry, the improvement comprising applying said pressure to essentially the entire surface of said pulp deposit with a hard and exible complementary shaped pressure exerting surface, exing each said pressure exerting surface after each adjacent mold has left said pulp slurry to permit air to enter between said pulp deposit and said pressure exerting surface, and removing said pressure exerting surface from said pulp deposit.

2. In a pulp molding apparatus including a pulp slurry vat, a series of shaped pulp molds mounted on carrier means to pass through said vat, a vacuum means for applying suction through said molds, and pressure applying means at least partially extending into said vat and into the slurry contained therein and provided adjacent and in facing relationship to said pulp molds at a position corresponding to a segment of the travel of said molds partially through said vat, and partially above said vat the improvement wherein said pressure applying means comprises a series of surfaces, each surface being shaped complementary to the shape of said pulp molds, said presure applying means further comprising aligning means Ifor maintaining said complementary surfaces in position and for urging each said complementary surface against a pulp deposit on a corresponding complementary mold, each said surface being hard and exible whereby said surface may ex for permitting air to enter between said pulp deposit and said surface to permit separation thereof.

3. A pulp molding apparatus as defined in claim 2 wherein said aligning means comprises chain sprockets and said pressure applying means further comprises a pair of endles chains passing about said chain prockets and `supporting therebetween said complementary surfaces.

4. A pulp molding apparatus in accordance with claim 3 wherein said chain sprockets are idle sprockets and said complementary pressure applying surfaces and said chains are driven about said sprockets by engagement of said complementary surfaces with said molds.

5. A pulp molding apparatus in accordance with claim 3 wherein two pair of chain sprockets are provided, one pair being disposed within said vat and said slurry and the other pair being disposed above said vat and adjacent said drum at the drum exit end of said vat, each of said endless chains being associated with one sprocket of each sprocket pair.

6. A pulp molding apparatus in accordance with claim Z wherein said hard and exible surface is formed of polyurethane.

7. An apparatus in accordance with claim 3 wherein each of said surfaces is connected to each of said endless chains at both the leading and trailing edges of each of said surfaces, said connection on said surfaces being provided through elongated slot means to permit said surfaces to pass about said sprockets and permit said surfaces to self-seat.

References Cited by the Examiner UNITED STATES PATENTS 2,699,733 9/ 1952 Honnig 162-227 3,167,469 1/1965 Wells 162-227 DONALL H. SYLVESTER, Primary Examiner.

I. H. NEWSOME, Assistant Examiner. 

1. IN THE METHOD OF SUCTION MOLDING PULP ARTICLES WHEREIN SERIES OF SHAPED PULP MOLDS IS PASSED THROUGH A VAT CONTAINING A SLURRY OF PULP AND WHEREIN VACUUM IS APPLIED TO THE MOLDS TO EFFECT THE DEPSOITION OF PULP THEREON AND COMPRISING APPLYING PRESSURE TO THE PULP DEPOSIT ON EACH SHAPED MOLD IN SEQUENCE WHILE SAID PULP DEPOSIT IS SUBMERGED BENEATH SAID PULP SLURRY, AND MAINTAINING APPLICATION OF PRESSURE UNTIL SAID MOLD HAS PASSED OUT OF SAID PULP SLURRY, THE IMPROVEMENT COMPRISING APPLYING SAID PRESSURE TO ESSENTIALLY THE ENTIRE SURFACE OF SAID PULP DEPOSIT WITH A HARD AND FLEXIBLE COMPLEMENTARY SHAPED PRESSURE EXERTING SURFACE, FLEXING EACH SAID PRESSURE EXERTING SURFACE AFTER EACH ADJACENT MOLD HAS LEFT SAID PULP SLURRY TO PERMIT AIR TO ENTER BETWEEN SAID PULP DEPOSIT AND SAID PRESSURE EXERTING SURFACE, AND REMOVING SAID PRESSURE EXERTING SURFACE FROM SAID PULP DEPOSIT.
 2. IN A PULP MOLDING APPARATUS INCLUDING A PULP SLURRY VAT, A SERIES OF SHARPED PULP MOLDS MOUNTED ON CARRIER MEANS TO PASS THROUGH SAID VAT, A VACUUM MEANS FOR APPLYING SUCTION THROUGH SAID MOLDS, AND PRESSURE APPLYING MEANS AT LEAST PARTIALLY EXTENDING INTO SAID VAT AND INTO THE SLURRY CONTAINED THEREIN AND PROVIDED ADJACENT AND IN FACING RELATIONSHIP TO SAID PULP MOLDS AT A POSITION CORRESPONDING TO A SEGMENT OF THE TRAVEL OF SAID MOLDS PARTIALLY THROUGH SAID VAT, AND PARTIALLY ABOVE SAID VAT THE IMPROVEMENT WHEREIN AND PRESSURE APPLYING MEANS COMPRISIES A SERIES OF SURFACES, EACH SURFACE BEING SHAPED COMPLEMENTARY TO THE SHAPE OF SAID PULP MOLDS, SAID PRESTURE APPLYING MEANS FURTHER COMPRISING ALIGNING MEANS FOR MAINTAINING SAID COMPLEMENTARY SURFACES IN POSITION AND FOR URGING EACH SAID COMPLEMENTAY SURFACE AGAINST A PULP DEPOSIT ON A CORRESPONDING COMPLEMENTARY MOLD, EACH SAID SURFACE BEING HARD AND FLEXIBLE WHEREBY SAID SURFACE MAY FLEX FOR PERMITTING AIR TO ENTER BETWEEN SAID PULP DEPOSIT AND SAID SURFACE TO PERMIT SEPARATION THEREOF. 